Rotor-stator structure for electrodynamic machines

ABSTRACT

A rotor-stator structure for electrodynamic machinery is disclosed to, among other things, minimize magnetic flux path lengths and to eliminate back-iron for increasing torque and/or efficiency per unit size (or unit weight) and for reducing manufacturing costs. In one embodiment, an exemplary rotor-stator structure can comprise a shaft defining an axis of rotation, and a rotor on which at least two substantially conical magnets are mounted on the shaft. The magnets include conical magnetic surfaces facing each other and confronting air gaps. In some embodiments, substantially straight field pole members can be arranged coaxially and have flux interaction surfaces formed at both ends of those field poles. Those surfaces are located adjacent to the confronting conical magnetic surfaces to define functioning air gaps. Current in coils wound on the field poles provide selectable magnetic fields that interact with magnet flux in flux interaction regions to provide torque to the shaft.

CROSS REFERENCE TO RELATED APPLICATION

This application is continuation of application Ser. No. 11/021,417,entitled “Rotor-Stator Structure for Electrodynamic Machines,” and filedon Dec. 23, 2004 now U.S. Pat. No. 7,061,152, which claims the benefitof U.S. Provisional Application No. 60/622,258, entitled “Rotor-StatorStructure for Electric Motors and Generators” and filed on Oct. 25,2004, the disclosure of which is incorporated herein by reference in itsentirety.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to electric motors, alternators,generators and the like, and more particularly, to a rotor-statorstructure for motors that, for example, increases output torque per unitsize (or per unit weight) either by minimizing the length of magneticflux paths or by straightening those paths through anisotropic fieldpole members, or both. Further, the rotor-stator structure conservesresources, such as reducing manufacturing costs, such as by minimizingwastage and by eliminating “back-iron” material.

BACKGROUND OF THE INVENTION

In traditional stator and rotor structures for fractional andsub-fractional horsepower motors, permanent magnets are often integratedinto a rotor assembly that typically rotates in the same plane as aferromagnetic stator structure that provides magnetic return paths formagnet and current-generated flux. Current-generated flux, which is alsoreferred to as Ampere Turn (“AT”)-generated flux, is generated bypassing a current through a coil winding that is wrapped about a poleregion of a stator member structure. While functional, conventionalstator and rotor structures of these and other electric motors haveseveral drawbacks, as are discussed next.

FIG. 1 illustrates a traditional electric motor exemplifyingcommonly-used stator and rotor structures. Electric motor 100 is acylindrical motor composed of a stator structure 104, a magnetic hub 106and a shaft 102. The rotor structure of motor 100 includes one or morepermanent magnets 110, all of which are attached via magnetic hub 106 toshaft 102 for rotation within stator structure 104. Stator structure 104typically includes field poles 118, each having a coil winding 112 (onlyone is shown) that is wound about each field pole 118. Stator structure104 includes slots 108 used in part to provide a wire passage forwinding coil wire about stator field poles 118 during manufacturing.Slots 108 also provide magnetic separation between adjacent field poles118. Stator structure 104 includes a peripheral flux-carrying segment119 as part of magnetic return path 116. In many cases, stator structure104 is composed of laminations 114, which typically are formed fromisotropic (e.g., non-grain oriented), magnetically permeable material.Magnetic return path 116, which is one of a number of magnetic returnpaths in which permanent magnet-generated flux and AT-generated flux ispresent, is shown as being somewhat arcuate in nature at peripheralflux-carrying segment 119 but includes relatively sharp turns into thefield pole regions 118.

One drawback of traditional electric motors, including electric motor100, is that magnetic return path 116 requires a relatively long lengthfor completing a magnetic circuit for flux emanating from one rotormagnet pole 110 and traversing via magnetic return path 116 to anotherrotor magnet pole 110. Furthermore, magnetic return path 116 is not astraight line, which is preferred for carrying magnetic flux. As shown,magnetic return path 116 has two ninety-degree turns in the stator path.Magnetic return path 116 turns once from field pole region 118 toperipheral flux-carrying segment 119, and then again from peripheralflux-carrying segment 119 to another field pole region 118. Both ofthese turns are suboptimal for carrying flux efficiently. Asimplemented, magnetic return path 116 requires more material, or“back-iron,” than otherwise is necessary for carrying such flux betweenfield poles. Consequently, magnetic return paths 116 add weight and sizeto traditional electric motors, thereby increasing the motor form factoras well as cost of materials to manufacture such motors.

Another drawback of conventional electric motors is that laminations 114do not effectively optimize the flux density in flux-carrying poles,such as through field poles 118 and stator regions at peripheralflux-carrying segment 119, due to hysteresis losses (or “iron losses”).Hysteresis is the tendency of a magnetic material to retain itsmagnetization. “Hysteresis loss” is the energy required to magnetize anddemagnetize the magnetic material constituting the stator regions,wherein hysteresis losses increase as the amount of magnetic materialincreases. As magnetic return path 116 has one or more turns ofninety-degrees or greater, the use of anisotropic materials, such asgrain-oriented materials, cannot effectively reduce hysteresis lossesbecause the magnetic return path 116 in peripheral flux-carrying segment119 would cut across the directional orientation of laminations 114. Forexample, if direction 120 represents the orientation of grains forlaminations 114, then at least two portions of magnetic return path 116traverse across direction 120 of the grain, thereby retarding the fluxdensity capacity of those portions of stator peripheral flux-carryingsegment 119. Consequently, anisotropic materials generally have not beenimplemented in structures similar to stator structure 104 since the fluxpaths are usually curvilinear rather than straight, which limits thebenefits provided by using such materials.

Yet another drawback of conventional electric motors is the relativelylong lengths of magnetic return path 116. Changing magnetic fields, suchas those developed at motor commutation frequencies, cause eddy currentsto develop in laminations 114 in an orientation opposing the magneticfield inducing it. Eddy currents result in power losses that are roughlyproportional to a power function of the rate at which the magnetic fluxchanges and roughly proportional to the volume of affected laminationmaterial.

Other drawbacks of commonly-used electric motors include theimplementation of specialized techniques for reducing “cogging,” ordetent torque, that are not well-suited for application with varioustypes of electric motor designs. Cogging is a non-uniform angular torqueresulting in “jerking” motions rather than a smooth rotational motion.This effect usually is most apparent at low speeds and applies additiveand subtractive torque to the load when field poles 118 are at differentangular positions relative to magnet poles. Further, the inherentrotational accelerations and decelerations cause audible vibrations.

In another type of electric motor, magnetic poles are positioned atrelatively large diameters about (or radial distances from) a rotorshaft. These magnetic poles, as well as the permanent magnets givingrise to those magnetic poles, are typically arranged coaxially about theshaft, with adjacent magnetic poles alternating in polarity. An armaturedisk usually supports the permanent magnets as separate, non-monolithicmagnets in a plane perpendicular to the rotor shaft. Structures such asthis are designed based on a certain tenet of electric motor design.According to this tenet, an increase in output torque is achieved byincreasing the radial distance between the magnetic poles and the rotorshaft. Consequently, the magnetic poles of this type of electric motorare increasingly being positioned at larger distances from the rotorshaft to increase the torque arm distance from the axis of rotation tothe air gaps, thereby increasing the output torque. A drawback to thisapproach is that additional materials are consumed in forming largermotor structures to accommodate the larger torque arm distance, such asthose structures that are used to form magnetic flux return paths. Thesemagnetic flux return paths are typically formed using “back-iron” tocomplete a larger flux path, which is generally circuitous in nature. Byadding back-iron to complete a magnetic circuit, the magnetic materialvolume through which the magnetic flux passes increases, whichdetrimentally tends to increase the hysteresis and eddy current losses,both of which can be collectively referred to as “core losses.” Further,the addition of back-iron to complete a magnetic circuit increases themagnetic flux path, thereby exacerbating core losses. Another drawbackto motors of this type is that the motor volume increases as themagnetic poles are positioned farther from the shaft, which in turn,limits the available applications and uses for this type of motor.

“Back-iron” is a term commonly used to describe a physical structure (aswell as the materials giving rise to that physical structure) that isoften used to complete an otherwise open magnetic circuit. Back-ironstructures are generally used only to transfer magnetic flux from onemagnetic circuit element to another, such as either from onemagnetically permeable field pole to another, or from a magnet pole of apermanent magnet to a magnet pole of another permanent magnet, or both.Further, “back-iron” structures are not generally formed to accept anassociated ampere-turn generating element, such as one or more coils.

In view of the foregoing, it would be desirable to provide arotor-stator structure that minimizes the above-mentioned drawbacks inelectric motors and generators, and to increase output torque andefficiency either on a per unit size or per unit weight basis, or both,as well as to conserve resources during manufacturing and/or operation.

SUMMARY OF THE INVENTION

A system, apparatus and method are disclosed for implementing anexemplary rotor-stator structure for use in electrodynamic machines,such as electric motors, generators, alternators, and the like.According to one embodiment of the present invention, a rotor-statorstructure for electrodynamic machines comprises conical magnets havingconical surfaces arranged axially on an axis of rotation such that theconical surfaces face each other. The conical magnets include at leasttwo conical magnets being positioned so that the directions ofpolarization of the two conical magnets are in substantially oppositedirections. Further, the rotor-stator structure can also include fieldpole members arranged coaxially to the axis. The field pole members haveflux interaction surfaces formed at the ends of the field pole membersand adjacent to portions of the conical surfaces that confront the fluxinteraction surfaces. The flux interaction surfaces define air gaps withthe portions of the conical surfaces and are configured to magneticallycouple the field pole members to the conical magnets. In some cases, therotor-stator structure includes a shaft on which the conical magnets areaffixed, the shaft defining the axis of rotation. The conical surfaceseach can have an angle of inclination from about 10 degrees to about 80degrees with respect to the axis of rotation. In one embodiment, each ofthe field pole members further comprises a magnetically permeablematerial that is continuous from one end of each field pole member tothe other end, where at least a portion of each field pole member isconfigured to accept an element, such as one or more coils, forgenerating ampere-turn (“AT”) flux. In an alternative embodiment, therotor-stator structure further comprises one or more coils, at least oneof which is wound about each of the field pole members to form activefield pole members. In some cases, the rotor-stator structure excludesback-iron, thereby decreasing hysteresis losses as well as materials formanufacturing an electrodynamic machine. In another embodiment, at leastone of the field pole members of a rotor-stator structure issubstantially straight. Substantially straight field pole members canprovide a relatively short magnetic flux path between magnets, which maybe accompanied by a reduction in the volume of the magneticallypermeable material as compared to the use of back-iron in sometraditional stator structures. By reducing the volume of magneticallypermeable material through which magnetic flux is conducted, hysteresislosses can be decreased.

The field pole members and the conical magnets of an exemplaryrotor-stator structure can be arranged to minimize linear deviations ina path portion of a magnetic flux path coincident with a substantiallystraight line extending from a surface portion of a first conical magnetto a surface portion of a second conical magnet, the path portionterminating at the surface portions. In a specific embodiment, therotor-stator structure is configured to generate magnetic flux pathsconsisting essentially of the first conical magnet, the second conicalmagnet, at least one of the field pole members, and two or more airgaps. The field pole members, in some instances, can compriselaminations to minimize eddy currents, thereby reducing power losses.The laminations can be formed from a substrate composed of amagnetically permeable material in a manner that reduces wastage of themagnetically permeable material. Notably, in certain instances, at leastone of the laminations is anisotropic, which can include grain-orientedmaterials. In one embodiment, the rotor-stator structure furthercomprises a coil wound about at least one of the field pole members toform at least one active field pole member, where at least the one fieldpole member is shaped to minimize manufacturing complexity associatedwith winding the coil on traditional field poles by obviating the needto wind the coil via a slot. In still another embodiment, each of theflux interaction surfaces further comprises a skewed flux interactionsurface to reduce field pole gaps between adjacent field pole members,thereby minimizing detent torque. Detent torque can also be reduced byoffsetting the directions of polarization of the two conical magnets byabout 150 to about 180 degrees. The field pole members, in at least oneexample of a rotor-stator structure, are stationary while the conicalmagnets can rotate relative to the field pole members, whereas in otherexamples, the conical magnets remain stationary and the field polemembers rotate relative to the conical magnets.

According to another embodiment of the present invention, a rotor-statorstructure for electrodynamic machines having an axis comprises a rotorhaving at least two substantially conical magnets arranged axially aboutthe axis. The two conical magnets can be spaced apart from each otherand can have regions of predetermined magnetic polarization. The magnetseach can have confronting conical magnetic surfaces of principaldimension that is substantially at an acute angle to the axis. Theconfronting conical magnetic surfaces face each other generally, withthe magnetic polarizations being in substantially opposite directions.The rotor-stator structure can also include field poles arranged coaxialto the axis and having flux interaction surfaces formed at the ends ofthe field poles. The flux interaction surfaces are typically locatedadjacent the confronting magnetic surfaces, which are generallycoextensive with the principal dimension thereof, defining functioningair gaps therewith. Each of the field pole members can be magneticallypermeable, wherein the flux interaction surfaces are configured tomagnetically couple the field pole members to the conical magnets. In atleast one instance, one or more field pole members each furthercomprises a coil about the one or more field pole members, therebyforming one or more active field pole members. In one embodiment, therotor-stator structure is configured to limit magnetic flux paths totraverse only through two of the conical magnets, the field polemembers, the flux interaction surfaces, and the air gaps. As such,back-iron is excluded. In a specific embodiment, the field pole memberscomprise one or more of silicon-iron alloys, nickel-iron alloys,cobalt-nickel alloys, magnetic-powdered alloys, and soft magneticcomposite, whereas the conical magnets can be permanent magnets composedof a magnet material having a recoil permeability less than 1.3 units asexpressed in units of the centimeter, the gram, and the second (“CGS”).As an example, the conical magnets can be composed of neodymium iron(“NdFe”), in whole or in part. As other example, the magnets can becomposed of ceramic, Samarium Cobalt (“SmCo”), or any other rare earthmagnet material.

According to yet another embodiment of the present invention, anexemplary rotor-stator structure for electrodynamic machines comprises ashaft defining an axis of rotation and having a first end portion, acentral portion and a second end portion. The rotor-stator structureincludes at least a first magnet having a surface contoured as at leasta portion of a cone to form a first conical surface, the first magnethaving a first direction of polarization and being disposed axially onthe shaft at the first end portion. Also, the rotor-stator structure caninclude a second magnet having a surface contoured as at least a portionof a cone to form a second conical surface, the second magnet having asecond direction of polarization and being disposed axially on the shaftat the second end portion such that the first direction of polarizationis substantially opposite to the second direction of polarization.Generally, the second conical surface faces, or confronts, the firstconical surface. The rotor-stator structure is further composed of anumber of field pole members arranged substantially coaxial to theshaft. Each of the field pole members comprises a number ofsubstantially straight laminations, at least one of which is composed ofanisotropic material and arranged in parallel with other laminations andin parallel with the axis of rotation. Each of the field pole membershas a first pole shoe at its first field pole member end and a secondpole shoe at its second field pole member end, the first pole shoe beingpositioned adjacent to a portion of the first conical surface to form afirst flux interaction region and the second pole shoe being positionedadjacent to a portion of the second conical surface to form a secondflux interaction region. Further, the rotor-stator structure includes atleast one coil wound about at least one of the number of field polemembers to form an active field pole member. As such, at least in somecases, the rotor-stator structure is configured to generate at least onemagnetic flux path limited to traverse only through the first magnet,the second magnet, the active field pole member and the first and secondflux interaction regions. In a specific embodiment, the at least onecoil extends substantially the length of the active field pole member inan axial direction for reducing flux leakage from the peripheries of theactive field pole member.

In an alternate embodiment, the first pole shoe and the second pole shoefurther comprise a first pole face and a second pole face, respectively,wherein at least a portion of the first pole face is contoured to form afirst air gap having a gap thickness principally defined by the distancebetween the portion of the first conical surface and the first poleface, and at least a portion of the second pole face is contoured toform a second air gap having a gap thickness principally defined by thedistance between the portion of the second conical surface and thesecond pole face. The gap thickness is generally no greater than 40% ofan average diameter of either the first magnet or the second magnet. Inanother embodiment, the first magnet and the second magnet each aredipole magnets oriented in a manner so their polarizations differ by anangle between 150 to 180 degrees, wherein each of the dipole magnets ismonolithic. In some embodiments, the first magnet and the second magneteach are multipole magnets. An exemplary configuration for arotor-stator includes three or four field poles and dipole magnets.Another configuration includes six or eight field poles configured tooperate with four-pole conical magnets. The rotor-stator structure, insome instances, can be configured to receive electrical power as anelectrical current into the at least one coil for implementing anelectric motor. In other instances, the rotor-stator structure can beconfigured to receive mechanical power as rotational motion about theshaft for implementing an electric generator.

According to still yet another embodiment of the present invention, anexemplary rotor-stator structure for electrodynamic machines comprises ashaft defining an axis of rotation, at least two permanent magnets eachhaving at least one conical surface and an outer surface, each of the atleast two permanent magnets being affixed coaxially on the shaft suchthat one of the at least one conical surface faces another, a pluralityof sets of coils, and a plurality of ferromagnetic field pole members.The plurality of ferromagnetic field pole members are disposedsubstantially parallel to the axis, each of the ferromagnetic field polemembers having a length along an axial direction, the lengthsubstantially extending at least between both of the at least oneconical surface of the at least two permanent magnets. Each of theferromagnetic field pole members also has at least a central portionaround which a set of coils of the plurality of sets of coils is wound.Each of the ferromagnetic field pole members has a pole shoe having atleast a pole face formed at each end of the ferromagnetic field polemembers. Each pole face is generally configured to form a fluxinteraction region with or via a portion of the at least one conicalsurface of either one of the at least two permanent magnets.

According to at least one embodiment, an exemplary rotor-statorstructure can be disposed within an electric motor to provide moreoutput torque deliverable by such a motor relative to conventionalelectric motors of the same size and/or weight. In one embodiment, arotor-stator structure provides a relatively shorter and straightermagnetic path, and a more efficient use of materials than traditionalstator-rotor structures for electrodynamic machines. In cases whereanisotropic (e.g., grain-oriented materials) lamination materials areused to form field pole members of specific embodiments of the presentinvention, the inherent magnetic properties of the laminationscontribute to an increase of flux density in flux-carrying regions. Theelimination or at least reduction in exterior return paths, such asthose return paths traditionally implemented using back-iron, thereforesaves weight and reduces the overall size of electrodynamic machinesimplementing various embodiments of the rotor-stator structure of thepresent invention. In another embodiment, a stator-rotor structureprovides a greater motor efficiency than a similarly-sized conventionalmotor with the same output torque. This efficiency increase is due, atleast in part, to lower resistance windings, which translates to lowercurrent-squared-times-resistance (i.e., I²*R) power losses whileproducing the same ampere turn-generated flux created in similarly-sizedpackages or motor housings of traditional motors. Further, therotor-stator structure of the present invention is less complex (e.g.,in the coil winding process) and less costly (e.g., due to conservationof materials) to manufacture than conventional motors.

BRIEF DESCRIPTION OF THE FIGURES

The invention is more fully appreciated in connection with the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 exemplifies commonly-used stator and rotor structures implementedin a traditional electric motor;

FIG. 2 is an exploded view of an exemplary rotor-stator structure inwhich the magnets are conical in shape, according to one embodiment ofthe present invention;

FIG. 3 depicts an end view for the rotor-stator structure of FIG. 2without a magnet to illustrate the orientation of the pole faces thatare configured to interact via an air gap with a confronting magneticsurface of a conical magnet, according to one embodiment of the presentinvention;

FIG. 4 depicts another end view for the rotor-stator structure of FIG. 2illustrating a conical magnet positioned adjacent to pole faces inaccordance with an embodiment of the present invention;

FIGS. 5A and 5B depict sectional views illustrating an exemplarymagnetic flux path, according to at least one embodiment of the presentinvention;

FIG. 5C depicts an example of a second flux path exiting a pole face ofa stator member generating an ampere-turn magnetic flux, according toone embodiment of the present invention;

FIG. 5D depicts an example of a second flux path(s) entering a pole faceof an active field pole member that originally generated the ampere-turnmagnetic flux of FIG. 5C, according to one embodiment of the presentinvention;

FIGS. 6A and 6B illustrate an end view of another exemplary rotor-statorstructure, according to another embodiment of the present invention;

FIG. 6C depicts a partial sectional view of the rotor-stator structureof FIGS. 6A and 6B, according to one embodiment of the presentinvention;

FIGS. 7A and 7B illustrate an exemplary field pole member, according toan embodiment of the present invention;

FIG. 8 illustrates another exemplary field pole member having skewedpole faces, according to a specific embodiment of the present invention;

FIGS. 9A to 9M illustrate examples of other-shaped permanent magnetsthat can be implemented in an exemplary rotor-stator structure,according to various embodiments of the present invention;

FIG. 10 shows a multiple pole magnet, according to an embodiment of thepresent invention; and

FIG. 11 shows another rotor-stator structure as an alternate embodimentof the present invention.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings. Note that most of the reference numeralsinclude one or two left-most digits that generally identify the figurethat first introduces that reference number.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Definitions

The following definitions apply to some of the elements described withrespect to some embodiments of the invention. These definitions maylikewise be expanded upon herein.

As used herein, the term “air gap” refers to a space, or a gap, betweena magnet surface and a confronting pole face. Such a space can bephysically described as a volume bounded at least by the areas of themagnet surface and the pole face. An air gap functions to enablerelative rotation between a rotor and a stator, and to define a fluxinteraction region. Although an air gap is typically filled with air, itneed not be so limiting.

As used herein, the term “back-iron” commonly describes a physicalstructure (as well as the materials giving rise to that physicalstructure) that is often used to complete an otherwise open magneticcircuit. In particular, back-iron structures are generally used only totransfer magnetic flux from one magnetic circuit element to another,such as either from one magnetically permeable field pole member toanother, or from a magnet pole of a first magnet to a magnet pole of asecond magnet, or both, without an intervening ampere-turn generatingelement, such as coil, between the field pole members or the magnetpoles. Furthermore, back-iron structures are not generally formed toaccept an associated ampere-turn generating element, such as one or morecoils.

As used herein, the term “coil” refers to an assemblage of successiveconvolutions of a conductor arranged to inductively couple to amagnetically permeable material to produce magnetic flux. In someembodiments, the term “coil” can be described as a “winding” or a “coilwinding.”

As used herein, the term “coil region” refers generally to a portion ofa field pole member around which a coil is wound.

As used herein, the term “core” refers to a portion of a field polemember where a coil is normally disposed between pole shoes and isgenerally composed of a magnetically permeable material for providing apart of a magnetic flux path.

As used herein, the term “field pole member” refers generally to anelement composed of a magnetically permeable material and beingconfigured to provide a structure around which a coil can be wound(i.e., the element is configured to receive a coil for purposes ofgenerating magnetic flux). In particular, a field pole member includes acore (i.e., core region) and at least two pole shoes, each of which isgenerally located near a respective end of the core. Without more, afield pole member is not configured to generate ampere-turn flux. Insome embodiments, the term “field pole member” can be describedgenerally as a “stator-core.”

As used herein, the term “active field pole member” refers to anassemblage of a core, one or more coils, and at least two pole shoes. Inparticular, an active field pole member can be described as a field polemember assembled with one or more coils for selectably generatingampere-turn flux. In some embodiments, the term “active field polemember” can be described generally as a “stator-core member.”

As used herein, the term “ferromagnetic material” refers to a materialthat generally exhibits hysteresis phenomena and whose permeability isdependent on the magnetizing force. Also, the term “ferromagneticmaterial” can also refer to a magnetically permeable material whoserelative permeability is greater than unity and depends upon themagnetizing force.

As used herein, the term “field interaction region” refers to a regionwhere the magnetic flux developed from two or more sources interactvectorially in a manner that can produce mechanical force and/or torquerelative to those sources. Generally, the term “flux interaction region”can be used interchangeably with the term “field interaction region.”Examples of such sources include field pole members, active field polemembers, and/or magnets, or portions thereof. Although a fieldinteraction region is often referred to in rotating machinery parlanceas an “air gap,” a field interaction region is a broader term thatdescribes a region in which magnetic flux from two or more sourcesinteract vectorially to produce mechanical force and/or torque relativeto those sources, and therefore is not limited to the definition of anair gap (i.e., not confined to a volume defined by the areas of themagnet surface and the pole face and planes extending from theperipheries between the two areas). For example, a field interactionregion (or at least a portion thereof) can be located internal to amagnet.

As used herein, the term “generator” generally refers to anelectrodynamic machine that is configured to convert mechanical energyinto electrical energy regardless of, for example, its output voltagewaveform. As an “alternator” can be defined similarly, the termgenerator includes alternators in its definition.

As used herein, the term “magnet” refers to a body that produces amagnetic field externally onto itself. As such, the term magnet includespermanent magnets, electromagnets, and the like.

As used herein, the term “motor” generally refers to an electrodynamicmachine that is configured to convert electrical energy into mechanicalenergy.

As used herein, the term “magnetically permeable” is a descriptive termthat generally refers to those materials having a magnetically definablerelationship between flux density (“B”) and applied magnetic field(“H”). Further, “magnetically permeable” is intended to be a broad termthat includes, without limitation, ferromagnetic materials, softmagnetic composites (“SMCs”), and the like.

As used herein, the term “pole face” refers to a surface of a pole shoethat faces at least a portion of the flux interaction region (as well asthe air gap), thereby forming one boundary of the flux interactionregion (as well as the air gap). In some embodiments, the term “poleface” can be described generally as a “stator surface.”

As used herein, the term “pole shoe” refers to that portion of a fieldpole member that facilitates positioning a pole face so that itconfronts a rotor (or a portion thereof), thereby serving to shape theair gap and control its reluctance. The pole shoes of a field polemember are generally located near each end of the core starting at ornear a coil region and terminating at the pole face. In someembodiments, the term “pole shoe” can be described generally as a“stator region.”

As used herein, the term “soft magnetic composites” (“SMCs”) refers tothose materials that are comprised, in part, of insulated magneticparticles, such as insulation-coated ferrous powder metal materials thatcan be molded to form an element of the rotor-stator structure of thepresent invention.

Discussion

FIG. 2 is an exploded view of an exemplary rotor-stator structure inaccordance with a specific embodiment of the present invention. In thisexample, rotor-stator structure 200 is configured to increase generatedtorque per unit size (or per unit weight) for electric motorimplementations either by minimizing the length of magnetic flux pathsor by straightening those paths through field pole members, or both. Insome embodiments, rotor-stator structure 200 implements straight pathsto provide a relatively low reluctance flux path inside those field polemembers as compared to conventional magnetic return path designs thatrequire magnetic flux to turn sharply, such as at an angle ofninety-degrees or greater, to enter field pole regions. Substantiallystraight field pole members also provide relatively short magnetic fluxpath portions between air gaps. As such, rotor-stator structures ofvarious embodiments of the present invention enable electrodynamicmachines to operate with low magnetic losses and increased efficiency.

In this example, rotor-stator structure 200 includes a rotor assembly202 and a number of active field pole members 204 (i.e., active fieldpole members 204 a, 204 b, and 204 c), whereby active field pole members204 are configured to magnetically couple to and drive magnets of rotorassembly 202. Rotor assembly 202 includes two conical magnets 220mounted on or affixed to a shaft 222 such that at least a portion of aconical magnet surface 221 a on conical magnet 220 a faces at least aportion of a conical magnet surface 221 b on conical magnet 220 b. Inparticular, the smaller diameter ends (i.e., nearest the cones vertices,conceptual or otherwise) of the conical magnets 220 face each other.Further, conical magnets 220 are each positioned adjacent to one groupof ends of active field pole members 204. In various embodiments of thepresent invention, conical magnet surfaces 221 a and 221 b each have anangle of inclination with respect to the axis of rotation, where theangle is from about 5 degrees to about 85 degrees. In a specificembodiment, the angle of inclination can be from about 10 degrees toabout 80 degrees. In at least one embodiment, the angle of inclinationis about 30 degrees with respect to the axis of rotation, for example,when conical magnets 220 are composed of relatively high performingmagnet material (e.g., magnets having relatively high values of maximumenergy product and “Br,” and high coercivity, as is discussed below).

Each of active field pole members 204 includes a field pole member 206and an insulated coil 208 wrapped around a respective field pole member206. Field pole members 206 are positioned coaxial about an axis ofrotation, which can be defined by the axis of shaft 222. Coils 208 a,208 b and 208 c are generally wound about the central portions of fieldpole members 206 a, 206 b and 206 c, respectively, to produce ampereturn-generated magnetic flux in field pole members 206 when the coils208 are energized with current. In at least one embodiment, one or moreactive field pole members 204 constitute, at least in part, a statorassembly (not shown). At each end region of active field pole members204 are pole faces 207, each of which is located adjacent to andconfronting at least a portion of the conical magnet surfaces of theconical magnets 220, thereby defining functional air gaps between magnetsurfaces (or portions thereof) and pole faces. According to a specificembodiment of the present invention, pole faces 207 are contoured tomimic the surfaces of a magnet, such as that of conical magnet 220 a.For example, pole face 207 b is a concave surface resembling thecurvature of that of a convex surface of conical magnet 220 a. In oneembodiment of the present invention, an optional extended end, such asan extended end 211 b, extends longitudinally from field pole members206 to extend over and/or past outer surfaces of conical magnets 220. Asanother example, extended end 217 b is configured to extend past theouter surface of conical magnet 220 b for insertion into one of grooves242 to construct rotor-stator structure 200.

As either rotor assembly 202 or the number of active field pole members204 can be configured to rotate in relation to the other, rotor-statorstructure 200 can optionally include bearings 230 and both a frontmounting plate 240 a and a rear mounting plate 240 b. In a specificembodiment, mounting plates 240 a and 240 b can be made of non-magneticand/or non-electrically conductive materials. Cavities 244 in mountingplates 240 a and 240 b are designed to receive bearings 230, and grooves242 are designed to receive at least a portion of an extended end, suchas extended end 217 b, of an active field pole member. In some cases,grooves 242 confine the movement of active field pole members 204 tomaintain a proper position with respect to rotor assembly 202. Aprotective housing (not shown) can be added to protect both rotorassembly 202 and field pole members 204 and can also serve as a heatsink for one or more coils 208.

Note that although each field pole member 206 is shown to be wrapped byinsulated coil 208, fewer than all of field pole members 206 can bewrapped by coil 208, according to a specific embodiment. For example,coils 208 b and 208 c can be omitted from active field pole members 204b and 204 c, respectively, to form an electrodynamic machine that, forexample, costs less to manufacture than if coils 208 b and 208 c wereincluded. Without coils 208 b and 208 c, members 204 b and 204 cconstitute field pole members rather than active field pole members.Also note that although field pole members 206 a, 206 b and 206 c areshown as straight field pole members, there is no requirement that fieldpole members 206 a, 206 b and 206 c be straight or substantiallystraight. In some embodiments, one or more of field pole members 206 a,206 b and 206 c can be shaped to implement non-straight field polemembers to convey flux in other than a straight flux path. For example,field pole members 206 a, 206 b and 206 c can be shaped to positioncoils 208 closer to shaft 222, thereby decreasing the volume of anelectrodynamic machine implementing rotor-stator structure 200.

FIG. 3 depicts an end view 300 of rotor-stator 200 illustratingorientation of the pole faces that are configured to interact via an airgap with a confronting magnetic surface of conical magnet 220 a,according to one embodiment of the present invention. Absent from FIG. 3is front mounting plate 240 a, bearings 230 and conical magnet 220 a,all of which are omitted to depict the end views of both the activefield pole member and coil shapes, as well as the field pole gaps (“G”)between the field poles. As shown, coils 208 a, 208 b, and 208 crespectively encompass field pole members 206 a, 206 b and 206 c to formactive field pole members 204 a, 204 b and 204 c, all of which arecompactly positioned to increase the packing density of a motor orgenerator implementing rotor-stator structure 200 (as compared toconventional motors using coil windings that typically are wound usingslots 108 of FIG. 1). FIG. 3 also depicts edges of extended ends 311 a,311 b, and 311 c, and pole faces 307 a, 207 b, and 207 c of respectiveactive field pole members 204 a, 204 b and 204 c. Pole faces 307 a, 207b, and 207 c are positioned to form magnetic air gaps between each ofthose pole faces, or surfaces, and at least a portion of the conicalmagnet surface of conical magnet 220 a. Further, field pole gaps aredefined by the sides (or edges) of the field pole members thatconstitute active field pole members 204 a, 204 b and 204 c. Forexample, gap “G” represents any of the field pole gaps as defined, forexample, by planes 310 and 320 extending from sides of respective fieldpole members 206 b and 206 c (FIG. 2).

FIG. 4 depicts another end view 400 of rotor-stator 200 and conicalmagnet 220 a positioned adjacent to pole faces 307 a, 207 b, and 207 c(FIG. 3) in accordance with an embodiment of the present invention. Asshown, outer magnet surface 223 a of conical magnet 220 a is visible, asare the protruding edges of extended ends 311 a, 311 b, and 311 c andcoils 208. Note that in this example, conical magnet 220 a is a dipolemagnet (e.g., a permanent magnet) having a north pole (“N”) and a southpole (“S”). Also, FIG. 4 defines three sectional views. The firstsectional view, X—X, cuts straight through as a centerline bisectingfield pole member 206 a and coil 208 a and then passes through a fieldpole gap between other field pole members 206 b and 206 c. A secondsection view, Y—Y, bisects field pole member 206 a and coil 208 a andthen passes through field pole member 206 b and coil 208 b. A third viewsection view, Y′—Y′, which is similar to the second section view, Y—Y,bisects field pole member 206 a and coil 208 a and then passes throughfield pole member 206 c and coil 208 c. Section view X—X is shown inFIG. 5A, whereas views Y—Y and Y′—Y′ produce similar drawings, both ofwhich are depicted in FIG. 5B.

FIGS. 5A and 5B depict sectional views illustrating an exemplarymagnetic flux path, according to at least one embodiment of the presentinvention. FIG. 5A depicts a cross section of active field pole member204 a of rotor-stator structure 500, the cross section showing asectional view X—X of coil 208 a and field pole member 206 a. In thisexample, active field pole member 204 a includes pole faces 307 a and505 b, pole shoes 507 a and 507 b, a coil region 506 and coil 208 a. Inview X—X of FIG. 5A, conical magnets 220 a and 220 b are diametricallymagnetized in opposite directions and are positioned adjacent torespective pole shoes 507 a and 507 b of field pole member 206.Correspondingly, pole face 307 a of pole shoe 507 a forms a magnetic airgap 551 a with at least a portion 521 a of magnet surface 221 a, withportion 521 a confronting pole face 307 a and shown as a cross-section.Similarly, pole face 505 b of pole shoe 507 b forms a magnetic air gap551 b with at least a portion 521 b of magnet surface 221 b, withportion 521 b confronting pole face 505 b and shown as a cross-section.Further, coil 208 a encloses a coil region 506 of field pole member 206a, whereby coil region 506 is defined approximately by the axial lengthof coil 208 a surrounding a portion of field pole member 206 a. Absentin FIG. 5A is a depiction of one or more field interaction regions,which can encompass a space larger than an air gap, such as air gap 551a, and can extend into, for example, conical magnet 220 a.

In at least one embodiment of the present invention, at least one ofmagnet surfaces 521 a and 521 b of respective conical magnets 220 a and220 b can be defined by an angle of inclination (“θ”) 501, which is anangle with respect to an axis of rotation. In the example shown, theaxis of rotation is coterminous with shaft 222. In a specificembodiment, angle of inclination (“θ”) 501 is 30 degrees from shaft 222.

With opposite polarizations, conical magnet 220 a is polarized with itsnorth pole (“N”) pointing in direction 502, and conical magnet 220 b ispolarized with its north pole (“N”) pointing in direction 504. In someembodiments, conical magnets 220 a and 220 b are diametricallymagnetized in exactly opposite directions (i.e., 180 degrees betweendirections 502 and 504). But in other embodiments, directions 502 and504 can be offset to any angle between those directions other than 180degrees, for example, to reduce detent torque (“cogging”). In a specificembodiment, directions 502 and 504 are offset to an angle between fromabout 150 degrees to about 180 degrees.

FIG. 5B depicts cross sections of active field pole member 204 a andeither active field pole member 204 b or active field pole member 204 c,and depicts a magnetic flux path, according to one embodiment of thepresent invention. For ease of discussion, only view Y—Y will bediscussed. View Y—Y is sectional view of coil 208 a and field pole 206 apassing though coil 208 b and field pole 206 b. Magnetic flux path 560passes through both field pole members 206 a and 206 b and through bothconical magnets 220 a and 220 b. For purposes of illustration, magneticflux path 560 (or flux path) may be described as comprising two fluxpaths that are combined by the principle of superposition. Conicalmagnets 220 a and 220 b form the first flux path (i.e., permanentmagnet-generated flux), whereas flux developed by amp-turns of the coilform the second flux path (i.e., ampere turn-generated flux). In thisexample, magnet flux as the first flux path exits the north pole (“N”)of conical magnet 220 a and crosses air gap 551 a to enter pole face 307a (FIG. 3), the north pole coinciding with surface portion 521 a, whichconfronts pole face 307 a. The first flux path then traverseslongitudinally through field pole member 206 a and then exits pole face505 b at the end of field pole member 206 a adjacent to conical magnet220 b. The first flux path continues by crossing air gap 551 b andenters the south pole (“S”) of conical magnet 220 b, the south polegenerally coinciding with a surface portion 521 b of magnet surface 221b and confronts pole face 505 b. The first flux path passes throughconical magnet 220 b to its north pole, which generally coincides with asurface portion 561 b of magnet surface 221 b that confronts pole face213 b. Next, the first flux path crosses air gap 551 c and enters poleface 213 b (FIG. 2). From there, the first flux path returns throughfield pole member 206 b to pole face 207 b from which it exits, crossesair gap 551 d, and then enters the south pole of conical magnet 220 a,thereby completing the first flux path. Generally, the south pole ofconical magnet 220 a coincides with a surface portion 561 a of magnetsurface 221 a (FIG. 2) that is confronting pole face 207 b. Note that inthe case shown, the flux exiting pole face 207 b is equivalent to thatflux exiting pole face 207 c. Note that no supplemental structure ormaterial need be required to form any portion of magnetic flux path 560.As such, rotor-stator structure 550 does not include back-iron.

In a specific embodiment, the diameters of conical magnets 220 are setso that the length of the flux path in each of conical magnets 220 isrelatively large with respect to the four air gaps 551 a to 551 d,thereby establishing a favorable magnet load line. Note that each of thefour air gaps 551 a to 551 d provides for a flux interaction region tofacilitate magnetic flux interaction between (or through) pole faces andthe magnet. Note further that a flux path in either conical magnet 220 aor 220 b is shown to align along the axis of magnetization (i.e., fromthe south pole to the north pole), which can contribute to low magnetmanufacturing costs and to magnets that can generate a relatively highoutput torque per unit volume (or size). The coercivity of the magnet,which is the property of the magnet that determines how well a magnetwill keep its internal flux alignment in the influence of strongexternal magnetic fields, can be optimally selected by using appropriatemagnet materials for a specific application.

In at least one embodiment, rotor-stator structure 550 (FIG. 5B)generates at least a portion of magnetic flux path 560 that extendssubstantially linearly from about surface portion 521 a of the magnetsurface of first conical magnet 220 a to about surface portion 521 b ofthe magnet surface of second conical magnet 220 b. In one instance, theportion of the magnetic flux path consists essentially of surfaceportion 521 a of first conical magnet 220 a, surface portion 521 b ofthe second conical magnet 220 b, at least one of the field pole members,such as field pole member 206 a, and two or more air gaps, such as airgaps 551 a and 551 b.

In at least one embodiment of the present invention, conical magnets 220a and 220 b can have at least the following two magnetic properties.First, conical magnet 220 a and 220 b are able to produce magnetic flux,such as measured in terms of flux density, “B,” with CGS units of Gauss.“CGS” refers to units described in terms of the centimeter, the gram,and the second. Second, the permanent magnet materials of conical magnet220 a and 220 b are such that the magnets resist demagnetization.Materials that have an ability to highly resist demagnetization areoften described as having “high coercivity,” as is well known in theart. Suitable values of demagnetizing fields can be used to drive aspecific magnet material flux density output to zero. As such, magnetmaterials that have relatively high values of coercivity generallyindicate that a magnet material is capable of withstanding large valuesof adverse external magnetic field intensities without sufferingdemagnetization effects. In a specific embodiment, conical magnet 220 aand 220 b are composed of magnet materials having a recoil permeabilityvalue relatively close to 1.00 and sufficient coercivity, Hd, underoperating conditions as to be reliable in reasonably expected conditionsof operation.

Magnet materials are often characterized in part by a maximum energyproduct of such materials. In addition, magnet materials may becharacterized by “Br,” which is the magnetic flux density output from amagnet material when measured in a closed circuit and no measuredexternal magnetic fields are being applied to that magnetic material.That maximum flux density value is frequently denoted as “Br.” A highvalue of Br indicates that a magnet material is capable of largemagnetic flux production per pole area (i.e., a high flux density). Inat least one embodiment, conical magnets 220 a and 220 b use magnetshaving high flux production capability (e.g., having high values of“Br”) in configurations where relatively high torque is desired inrelatively small device volumes.

In various embodiments, conical magnets 220 a and 220 b (or otherpermanent magnets) use high-valued Br magnets that can be relativelyshort in the axial direction and use a cone angle of about 30 degrees,for example, from the axis of rotation. But in some embodiments, conicalmagnets 220 a and 220 b (or other magnets suitable for practicing thepresent invention) use magnet materials having lower cost and lowervalues of Br. In this case, the magnets generally are implemented withan air gap having a relatively larger area than those associated withhigher values of Br. In particular, an increased area for an air gap isformed by increasing the axial length of a magnet, thereby increasingthe surface area of a magnetic surface confronting a respective poleface. As such, lesser cone angles (e.g., less than 30 degrees) in a sameouter diameter device (e.g., motor housing) can be used, albeit longerin the axial direction. Although the output torque performance, and Km,can remain the same over many embodiments, the manufacturing cost can beless in the low-valued Br version even though there can be an increasein axial length.

While various embodiments of the present invention cover a multitude ofdesign motor and/or generator designs using any of known availablemagnet materials, at least one embodiment uses magnet materials with lowratios of values of B to values of adverse applied field intensity, suchratios, as is typically specified in many magnet material data sheets,being measured at the respective material's Br point, those ratiosdefining the “recoil permeability at Br” of such materials. While insome cases magnet materials need not only be limited to high values ofcoercivity, the magnet materials should exhibit predictable output fluxdensities when subjected to expected adverse magnetic field or thermalconditions. As such, the value of “recoil permeability” can be at leastone factor when considering a motor and/or generator design using anexemplary rotor-stator structure, according to one embodiment of thepresent invention.

Recoil permeability is generally an expression of the relationshipbetween values of B and the values of adverse applied field intensity.The values of recoil permeability are typically evaluated in terms ofCGS units (because the permeability of air is 1.0 in CGS units) and canbe determined by dividing a value of B (e.g., expressed in Gauss), nearor at Br, by a value of adverse applied field intensity (e.g., H, nearor at Hc, expressed in Oerstead). For some magnet materials, an averagerecoil permeability value can be determined and may be useful in magnetmaterial selection. In one embodiment, recoil permeability can bedefined for various magnetic materials by Magnetic Materials ProducersAssociation (“MMPA”) Standard 0100-00, as maintained by theInternational Magnetics Association (“IMA”). Note that recoilpermeability can also be described in terms of MKS units (i.e., meter,kilogram, and second).

Generally, values of recoil permeability are not less than one whenexpressed in CGS units. The closer that a recoil permeability value isto 1.0, however, the higher the coercivity can be for a specificmeasured material. In most embodiments of the present invention, a valueof recoil permeability is typically less than 1.3. Typicalhigh-coercivity magnet materials, such as magnets composed ofneodymium-iron (“NdFe”) and variants thereof, can have a recoilpermeability value of about 1.04 in CGS units. An example of such avariant is Neodymium-Iron-Boron, or “NdFeB.” Common low-cost ceramicmagnets, such as those composed of ferrite ceramic, can have a ratiovalue of about 1.25, which permits ceramic magnets to perform adequatelyin most applications. Note that the average recoil permeability oftypical high performance ceramic magnets is usually within a range of1.06 to 1.2 in CGS units, more or less.

Coils 208 wound around each of field pole members 206 form the secondflux path. In this example, the flux generated by the ampere-turns incoils 208 a and 208 b of FIG. 5B travels in a similar path to thepermanent magnet flux, with the exception that conical magnets 220 a and220 b have effective properties similar to that of air as viewed by theampere turn-generated flux. As such, the ampere-turn flux generatedwithin field pole member 206 a (e.g., within coil region 506) is presentat a pole face adjacent to conical magnet 220 b of FIGS. 5A and 5B.

FIG. 5C depicts an example of a second flux path exiting a pole face ofthe active field pole member that generates that ampere-turn magneticflux, according to one embodiment of the present invention. In thisfigure, ampere-turn (“AT”)-generated flux is generated in active fieldpole member 204 a and then exits from pole face 513 a by dividingapproximately in half to form flux 570 a and 570 b. Then, ampere-turnflux 570 a enters pole face 213 b, and ampere-turn flux 570 b enterspole face 513 c. Then, respective portions of the second flux path thentravel longitudinally through the other field pole members (e.g., fieldpole members 206 b and 206 c) to the other ends of those other fieldpole members to return to active field pole member 204 a, whichinitially generated the second flux path.

FIG. 5D depicts an example of the second flux path(s) returning to apole face of the active field pole member that generated the ampere-turnmagnetic flux, according to one embodiment of the present invention. Asshown, ampere-turn magnetic flux 570 c and 570 d exit respective polefaces 207 b and 207 c to enter pole face 307 a, thereby completing themagnetic circuit of the second flux path (i.e., the ampere-turn magneticflux path).

Conceptually, the magnetic fields generated by the ampere-turns in eachfield pole member of active field pole members 204 a, 204 b, and 204 ccan be viewed as regions of magnetic potential at each of the pole facesat the end regions or pole shoes of the active field pole members. Inthe air gaps between the confronting surfaces of the conical magnets andtheir adjacent pole faces, the flux of the first flux path and the fluxof the second flux path interact in a manner familiar to those skilledin the art, where such an interaction is useful to generate torque by anelectric motor implementing rotor-stator structure 200, according to atleast one embodiment of the present invention. The first and the secondflux paths of rotor-stator structure 200 are efficient, at least inpart, because the flux is contained within the core regions 506 (FIG.5A) of field pole members 206 by the currents running through coils 208.The magnet flux generated by each of the conical magnets 220 interactsin a flux interaction region with the magnetic flux from pole faces ofactive field pole members 204. As such, flux leakage paths, if any, aregenerally limited to relatively very small regions at pole shoes 507 aand 507 b (FIG. 5A), both of which include the sides and the backs offield pole members 206. As the first and second flux paths are alsomostly straight in the magnetically permeable material of field polemembers 206, these field pole members are well suited to be implementedwith anisotropic (e.g., grain-oriented), magnetic materials in anefficient manner. As such, field pole members 206 can be composed of anyanisotropic, magnetic materials capable of carrying higher fluxdensities and lowering magnetic losses in the direction of magneticorientation, such as along the grains of grain-oriented materials, ascompared to the use of isotropic, non-grain oriented, magneticmaterials.

To illustrate, consider that an exemplary anisotropic (e.g.,grain-oriented) material can have a magnetic saturation value of 20,000Gauss, whereas a typical isotropic lamination material, such as “M19”laminations, have a saturation value of 19,600 Gauss. Moreover, theapplied field required for the anisotropic material to reach saturationis only 126 Oerstead as compared to 460 Oerstead for the isotropicmaterial. Core losses for the anisotropic grain-oriented material (e.g.,laminations of 0.014 inch thick) can be about 0.66 Watts per pound at 60Hz with 15,000 Gauss induction. By contrast, a typical isotropicmaterial can have core losses of about 1.64 Watts per pound undersimilar conditions. In view of the foregoing, the use of anisotropicmaterials in forming field pole members 206 is advantageous over the useof isotropic materials. According to at least one embodiment, thesubstantially straight shape of field pole members 206 enables effectiveuse of anisotropic materials, unlike magnetic flux paths of traditionalmotors.

Unlike output torque generation of conventional motors, the outputtorque generated by rotor-stator structures 200 of various embodimentsof the present invention need not be proportional to the radius from theaxis of rotation on shaft 222 to the active air gaps 551 a to 551 d(FIG. 5B). All other factors being the same, increasing the radialdistance of the pole faces and air gaps from shaft 222 does not changethe output torque in the way that traditional motor design formulasindicate. For example, traditional motor design concepts teach that theregions carrying ampere-turn flux should be designed to have lowreluctance paths, including the part of the ampere-turn magnetic fluxpath that is the air gap. According to various embodiments of thepresent invention, the ampere-turn flux path has a relatively highreluctance path through the space occupied by permanent magnets, such asconical magnets 220, yet peak torque production is relatively high incomparison to that of most traditional motors of the same size or weight(again, with other factors being equal). In a specific embodiment, themagnet materials that constitute conical magnets 220 have a magnetpermeability value similar to that of air, and as such, the volume ofeach conical magnet 220 appears as an additional air gap to theampere-turn magnetic circuit. In at least one embodiment, the outputtorque generated by an electrodynamic machine is proportional, in wholeor in part, to the volumes of conical magnets 220.

In operation of rotor-stator structure 200, coils 208 are sequentiallyenergized to cause rotation of rotor assembly 202. The energized coilsgenerate magnetic potentials at the pole faces. These magneticpotentials tend to re-orient the internal field directions of themagnets (e.g., conical magnets 220) to the direction of the appliedexternal field. The external field, in effect, presents anangularly-directed demagnetizing field to conical magnets 220 such thatthe demagnetizing field is capable of reaching relatively largeamplitudes when a motor implementing rotor-stator structure 200 is underhigh torque loads. The intense demagnetizing field can detrimentallyre-magnetize magnet materials of conical magnets 220 that haveinsufficient coercivity. For this reason, at least one embodiment of thepresent invention uses magnet materials suited for high torque loadingand have: (1) a low B-to-adverse-applied-field intensity ratio, and (2)a relatively low recoil permeability, such as less than 1.3 in CGSunits, for example.

In an embodiment of the present invention, the produced torque isthrough the natural inclination of the magnets, such as conical magnets220, to seek the lowest energy position. Accordingly, the magnet polesof conical magnets 220, which can be permanent magnets, tend to rotatetoward regions of greatest magnetic attraction and away from regions ofmagnetic repulsion, whereby such regions of “magnetic potential” arecreated at the air gaps at both ends of energized active field polemembers 204 by the ampere-turn generated magnetic fields. Since a magnethaving a relatively high coercivity will resist attempts to angularlydisplace the direction of its internal magnetic field, this resistanceto angular displacement is manifested as mechanical torque on the bodyof the permanent magnet, thereby transferring torque to the shaft. Assuch, the magnets (e.g., conical magnets 220) can develop and thentransfer torque to the shaft as useful output torque applied to a load.

FIGS. 6A, 6B and 6C illustrate an end view 600 of another exemplaryrotor-stator structure, according to another embodiment of the presentinvention. FIGS. 6A and 6B show end views 600 of a rotor-statorstructure while FIG. 6C is a partial sectional view A—A of FIG. 6B. FIG.6A shows active field pole members 604 each having a skewed pole face607 at an end of a respective field pole member 606. Each skewed poleface 607 has a contoured surface that generally tracks the surfacecharacteristics of that of a confronting surface portion of an adjacentmagnet, such as conical magnet 220 a, to form an air gap having, forexample, a relatively constant air gap thickness. Air gap thicknessgenerally refers to the orthogonal distance between a pole face and aconfronting surface of a magnet. The skewed pole faces 607 are, at leastin part, defined by surface edges and/or sides of field pole members 606that are slightly angled or skewed with respect to the polarity of anadjacent magnet. Skewed edges and/or sides are shown in FIG. 6A as firstskewed edges 650 and second skewed edges 652, both of which areconfigured as edges of field pole members 606 to form skewed field polegaps 660 when active field pole members 604 are arranged in arotor-stator structure. As an example, consider that first skewed edge650 c is configured to form an angle 622 with respect to at least onedirection of polarization 630 of a magnet (not shown). Consider furtherthat second skewed edge 652 b is configured to form an angle 620 withrespect to direction of polarization 630. Angles 620, 622 can be thesame angle or can be any other angle that is suitable for forming fieldpole gaps 660 that are skewed in relation to the directions ofpolarization of one or more magnets. Note that FIG. 6C is a partialsectional view showing skewed edges being configured so that the radialplane of magnetic polarization 631 does not align with either of fieldpole edge 650 or field pole edge 652. In particular, field pole edge 650c and field pole edge 652 b both do not align (i.e., are skewed)relative to plane of magnetization 631.

FIG. 6B is an end view 670 showing skewed pole face edges at both endsof field pole members 606. By implementing skewed field pole gaps 660 ina rotor-stator structure, detent torque (“cogging”) is reduced. In atleast one embodiment, skewed field pole gaps 660 are adapted for usewith permanent magnets that are diametrically polarized, such as conicalmagnets 220. In this instance, end view 670 is an end view showing polefaces 607 that are configured to surface contours similar to that of anadjacent conical magnet 220 a, pole faces 607 being similar to thoseshown in FIG. 6A. Also shown in FIG. 6B are first skewed edges 680 andsecond skewed edges 682, which are associated with pole faces at theother end of field pole members 606 (e.g., at the other pole shoeopposite than that associated with first skewed edges 650 and secondskewed edges 652). First skewed edges 680 and second skewed edges 682 inthis case have angles similar to those of first skewed edges 650 andsecond skewed edges 652, respectively, but face a magnet surfaceassociated with conical magnet 220 b, for example. As such, the angulardirections of the field pole gaps formed by edges 650 and 652 areopposite in the angular direction of the field pole gaps formed by edges680 and 682. Consequently, the diametrically polarized magnets willgenerally not align with a field pole gap having pole face sides similarto those that form field pole gap “G” between planes 310 and 320 (FIG.3), which can be a source of cogging torque in an electric motor. Notethat distance between edges 650 and 652, as well as between edges 680and 682, can be configured to be as narrow as necessary to minimize thecogging effects of the field pole gaps.

FIGS. 7A and 7B illustrate an exemplary field pole member, according toone embodiment of the present invention. Although each of field polemembers 206 a, 206 b, and 206 c can be composed of a single piece ofmagnetically permeable material (e.g., a piece formed by a metalinjection molding process, forging, casting or any other method ofmanufacture), these field pole members can also be composed of multiplepieces, as is shown in FIGS. 7A and 7B. FIG. 7A depicts one of fieldpole members 206 as a stacked field pole member 700 composed of a numberof laminations 704 integrated together. In this instance, stacked fieldpole member 700 has an outer surface 702 having a cylindrical outsidediameter with an arc and a relatively straight inner surface 706 toincrease the coil packing density while still leaving room for therotating shaft. Field pole member end regions 720 generally include polefaces 707 for interacting with the flux of permanent magnets at each endof field pole member 700, whereas a central portion 722 generallyincludes a core region between pole faces 707, such as coil region 506(FIG. 5A). A coil (not shown) can be wound more or less about centralportion 722. FIG. 7B is a perspective view of stacked field pole member700 and laminations 704, which are composed of an anisotropic material.In this example, the anisotropic material includes grain-orientedmaterial.

Note that various winding patterns can be implemented to enhanceperformance. For example, a cantered or full-coverage winding can coversubstantially all of the sides and/or the back of field pole member 700,at both ends of the structure, to reduce the flux that might leak fromone field pole member to another. As such, the wire of a coil need notbe wound perpendicular to the long axis of the field pole member, but atan oblique angle. With coils being placed close to the magnetic air gap,those coils can be more effective in reducing flux leakage.

FIG. 8 illustrates another exemplary field pole member having skewedpole faces, according to a specific embodiment of the present invention.As shown, stacked field pole member 800 is constructed from a number oflaminations 804, similar to stacked field pole member 700. Laminations804 are patterned to provide skewed pole faces 807. Pole face 807 isbound by both a first skewed edge 850 and a second skewed edge 852,whereas the other pole face 807 at the other pole shoe is bound by afirst skewed edge 880 and a second skewed edge 882. Note that edges 850,852, 880 and 882 can respectively correspond to edges 650, 652, 680, and682 of FIG. 6B. In some cases, laminations 804 (as well as laminations704) advantageously can be formed (e.g., stamped out) in a series ofeither similarly or differently patterned shapes from a single substrate(e.g., a sheet of metal or the like) in a manner that minimizes wasteduring manufacturing (i.e., almost all of the starting material can beefficiently utilized as an optimum number and/or size of laminations persubstrate can be selected). Further, the manufacture of laminations 704and 804 does not waste materials typically jettisoned to create circularholes in circular stator structures.

In some embodiments, laminations 704 and 804 can be assembled fromlaminated anisotropic (e.g., grain-oriented) sheet stock with thedirection of magnetic orientation being oriented longitudinally, such asparallel to an axis of rotation. This is so that flux can be easilyconducted axially from one end of the motor to the other. Thelaminations can be electrically insulated from each other, which canreduce eddy current losses. In one embodiment, laminations 704 and 804are composed of grain-oriented steel and provide various field polemembers with high permeability, low loss and/or high saturation levelsin a relatively low cost material. One type of anisotropic materialsuitable for implementing laminations 704 and 804 iscold-rolled-grain-oriented steel, or “CRGO lamination steel.” Toillustrate the advantages of using grain-oriented lamination inaccordance with at least one embodiment, cold rolled grain orientedsteel can have a permeability of 50,000 while subjected to an appliedfield of 10,000 Gauss in comparison to commonly-used isotropic laminatesteel (e.g., “M19” laminates) having a permeability of about 5950, underthe same conditions. Note that permeability, as described above, is interms of direct current (“DC”) permeability. Field pole members can bemade from many different magnetically permeable materials, such assilicon iron alloys, nickel iron alloys, cobalt nickel alloys, magneticpowdered alloys, soft magnetic composites, and the like, according tovarious embodiments of the present invention. Soft magnetic compositematerials, which are also known as “SMC materials,” are composed ofcompacted, electrically insulated particles that are also magneticallypermeable. As such, SMC materials exhibit relatively low eddy currentlosses when compared to traditional SiFe lamination materials atrelatively high frequencies. Another significant advantage of SMCmaterials is its ability to be formed in three dimensions through use ofproperly designed compaction molds and dies.

FIGS. 9A to 9M illustrate examples of other-shaped permanent magnetsthat can be implemented in a rotor-stator structure, according tovarious embodiments of the present invention. Although the permanentmagnets shown in FIG. 2 are conical in shape, the term “conical” isintended to be construed broadly to include one or more shapes that formone or more surfaces, or portions thereof, that when coaxially mountedon a shaft, are at an angle to the shaft such that at least one surface,when extended, would intersect an axis of rotation. So, the term“conical magnet” is meant to cover any configuration of magnet that hasat least a portion of a surface that is conical or tapered toward apoint coaxial with, or on, an axis of rotation. For example, at leastone type of conical magnet has one or more surfaces whereby thecross-sections of the magnet at each of those surfaces generally (or onaverage) either increase or decrease progressively along the axiallength of the magnet. In at least one specific embodiment, a relevantdimension for describing a portion of conical magnet surface is asurface boundary, such as a contoured surface area that can be orientedin space with respect to a line.

FIG. 9A shows a full cone-shaped magnet as an example of a conicalmagnet, whereas FIG. 9B depicts a conical magnet being a truncated conemagnet described as a “frustum of a right circular cone,” which is afrustum created by slicing the top off a right circular cone (e.g., theslice forming an upper base parallel to the lower base, or outersurface, of the right circular conical magnet). Note that other coneangles can be used other than is shown in FIG. 9A. FIG. 9C shows that aconical magnet can include cylindrical portions added to the largediameter end (or, in some cases, to the small diameter end, such asshown in FIG. 9I) to optimize magnetic flux in the circuit. FIG. 9Dillustrates a conical magnet being of a “stepped” or graduated form.FIGS. 9E and 9F show examples of alternative shapes suitable forimplementing a permanent magnet in accordance with embodiments of thepresent invention, where a conical magnet can be ahemispherically-shaped magnet. FIGS. 9G and 9H are generalrepresentations showing that conical magnets of various embodiments canhave any type of concave surface and any type of convex surface,respectively.

FIG. 9I shows an exemplary conical magnet in accordance with oneembodiment of the present invention. Here, conical magnet 940 includesan outer surface 950 in which a cavity 952 is formed. Cavity 952 isoptional and can be used to house bearings or the like. In someembodiments, cavity 952 extends through cylindrical surfaces 954 and958. Conical magnet 940 includes three surfaces: a first cylindricalsurface 954, a conical surface 956 and a second cylindrical surface 958.In various embodiments, conical magnet 940 can include: fewer or moresurfaces, cylindrical surfaces having larger or small diameters, steeperor shallower angles of inclination for conical surface 956, etc. FIGS.9J and 9K show an end view and a side view, respectively, of anexemplary conical magnet, according to one embodiment of the presentinvention. Conical magnet 971 is composed of two conical magnets 970 and972. In this example, conical magnet 972 is disposed (e.g., inserted)within conical magnet 970. In one embodiment, conical magnet 970 iscomposed of NdFe magnetic material (or a variant thereof) and conicalmagnet 972 is composed of a ceramic magnetic material.

FIGS. 9L and 9M illustrate yet other conical magnets in accordance withyet other embodiments of the present invention. FIG. 9L illustrates apyramidal-shaped magnet as a conical magnet, albeit truncated, formedwith any number of truncated triangular surfaces 978. FIG. 9Millustrates a conical magnet 980 of at least one embodiment, whereconical magnet 980 includes a truncated pyramidal magnet 990 includingmagnetic regions 992 formed either therein or thereon. Magnetic regions992 include magnetic material that is different that that of truncatedpyramidal magnet 990. Each of those magnetic regions 992 can be selectedto have any predetermined polarity. In one embodiment, truncatedpyramidal magnet 990 is four-sided and is composed of a ceramic material(e.g., magnetic material), and each magnetic region 992 (two of whichare hidden from view) is composed of NdFe magnetic material and areformed upon truncated pyramidal magnet 990. In other embodiments,pyramidal magnet 990 can have any number of sides.

In a specific embodiment of the present invention, conical magnets areanisotropic, diametrically magnetized, and shaped as a truncated conewith about 30 degrees of cone angle relative to an axis of rotation. Atleast one advantage of this magnet configuration is that such diametricconical magnets can be magnetized in the same direction as the originalmagnetic orientation of the magnet material, which provides a higherenergy product for the magnet (i.e., a more powerful magnet).Anisotropic magnets are also relatively easy to manufacture and haverelatively high magnetic efficiency per unit magnet volume. Anotheradvantage of a diametric (i.e., 2 pole) magnet is that in a motor havingthree active field pole members and three phases, there can be only oneelectrical revolution for each mechanical revolution of the motor.Accordingly, the diametric magnet, in whole or in part, reduces eddycurrent losses, hysteresis (“core” or “iron”) losses and electricalswitching losses in a motor drive circuit. In some embodiments, aconical magnet can: (1) include a steel core instead of being solidmagnet material, (2) be constructed from ring magnets exhibiting goodcoercivity, (3) be constructed from arc-segment magnets, (4) be moldeddirectly onto the shaft, (5) be radially polarized, (6) include a hollowcore instead of being solid magnet material, or can include any othersimilar characteristics.

FIG. 10 shows a multiple pole magnet, according to one embodiment of thepresent invention. In this example, permanent magnet 1000 is a four-polemagnet being magnetically oriented to have arcuate magnetic paths 1010from south poles (“S”) to north poles (“N”). Other numbered poles andmagnet orientations are within the scope and spirit of the presentinvention. As used herein, the term “monolithic” as applied to apermanent magnet, suggests that the permanent magnet is composed ofintegrated magnetic poles, such that the permanent magnet isnon-discrete and is substantially homogenous in structure. As such, amonolithic permanent magnet lacks any interfaces between the magneticpoles. A monolithic magnet therefore is composed of continuous magnetmaterial. By contrast, permanent magnet 1000 can be composed of separatemagnets (i.e., non-monolithic), each contributing an outward facingnorth or south pole, whereby interfaces exist between separatesubcomponents. As such, a non-monolithic magnet therefore is composed ofnoncontinuous magnet material. Note that the term “monolithic” can alsoapply to field pole members and active field pole members.

FIG. 11 shows rotor-stator structure 1100 as an alternate embodiment ofthe present invention. Generally, a quantity of three active field polemembers efficiently uses a cylindrical volume or space that is typicallyavailable inside the motor or generator. As such, “three” active fieldpole members are generally used to provide a relatively high packingdensity. But to provide more balanced operation, more than three activefield pole members can be used. As shown, six active field pole members1102 are arranged coaxially to and positioned equidistantly about anaxis of rotation. Also, a four-pole magnet 1104 is positioned adjacentto the pole faces of active field pole members 1102. In this instance,four-pole magnet 1104 is a composite of individual magnet arc-segments.Rotor-stator structure 1100 can provide more balance magneticallyrelative to rotor-stator structures that include three active field polemembers, because coils of opposing active field pole members 1102 cangenerally be excited at the same time. Other numbers of active fieldpole members and other even numbers of magnet poles can suitably becombined to implement rotor-stator structures of the present invention.

In one embodiment of the present invention, an exemplary rotor-statorstructure is disposed in an electrical motor to generate a torqueamplitude that depends on the volume of the magnets, the vectordirections of the interacting fields in the flux interaction regions,the flux density in flux interaction regions, the area of the air gaps,and the area of the pole faces. So, the higher the flux density producedby the permanent magnets and the higher the flux density produced by theactive field pole members, the higher the torque that will be developeduntil significant saturation is reached in the field pole members. Themagnet materials of such a rotor-stator structure should have sufficientcoercivity to prevent partial or total demagnetization in an intendedapplication.

A practitioner of ordinary skill in the art requires no additionalexplanation in making and using the embodiments of the rotor-statorstructure described herein but may nevertheless find some helpfulguidance by examining the following references in order from most toleast preferred: “IEEE 100: The Authoritative Dictionary of IEEEStandard Terms,”Institute of Electrical and Electronics Engineers (KimBreitfelder and Don Messina, eds., 7th ed. 2000), “General MotorTerminology,” as defined by the Small Motor and Motion Association(“SMMA”), and “Standard Specifications for Permanent Magnet Materials:Magnetic Materials Producers Association (“MMPA”) Standard No. 0100-00,”International Magnetics Association.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that specificdetails are not required in order to practice the invention. In fact,this description should not be read to limit any feature or aspect ofthe present invention to any embodiment; rather features and aspects ofone embodiment may readily be interchanged with other embodiments. Forexample, although the above description of the embodiments related to amotor, the discussion is applicable to all electrodynamic machines, suchas a generator. Thus, the foregoing descriptions of specific embodimentsof the invention are presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed; obviously, many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications; they therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. Notably, not every benefit described hereinneed be realized by each embodiment of the present invention; rather anyspecific embodiment can provide one or more of the advantages discussedabove. It is intended that the following claims and their equivalentsdefine the scope of the invention.

1. A rotor-stator structure for electrodynamic machines comprising: ashaft defining an axis of rotation and having a first end portion, acentral portion and a second end portion; a first magnet having asurface contoured as at least a portion of a cone to form a firstconical surface, said first magnet being disposed axially on said shaftat said first end portion; a second magnet having a surface contoured asat least a portion of a cone to form a second conical surface, saidsecond magnet being disposed axially on said shaft at said second endportion, said second conical surface facing said first conical surface;a number of field pole members arranged substantially coaxial to saidshaft, each of said field pole members comprising a number oflaminations arranged substantially in parallel with other laminationsand substantially in parallel with said axis of rotation, each of saidfield pole members having a first pole shoe at a first field pole memberend and a second pole shoe at a second field pole member end, said firstpole shoe being positioned adjacent to a portion of said first conicalsurface to form a first flux interaction region and said second poleshoe being positioned adjacent to a portion of said second conicalsurface to form a second flux interaction region; and at least one coilwound about at least one of said number of field ode members to form anactive field pole member.
 2. The rotor-stator structure of claim 1wherein said number of field pole members comprises at least on fieldpole member that includes substantially straight laminations formed froman anisotropic material.
 3. The rotor-stator structure of claim 1wherein each of said field pole members is an elongated field polemember having a length dimension in an axial direction greater than awidth dimension.
 4. The rotor-stator structure of claim 1 wherein saidfirst magnet and said second magnet rotate about said axis relative tosaid number of field pole members, which are stationary.
 5. Therotor-stator structure of claim 1 wherein said first magnet and saidsecond magnet are permanent magnets comprising neodymium iron (“NdFe”).6. The rotor-stator structure of claim 1 wherein said first fluxinteraction region, said second flux interaction, said first magnet,said second magnet and said field pole members are sufficient to form aclosed flux path.
 7. The rotor-stator structure of claim 6 wherein saidclosed flux path passes through at least two of said field pole membersin different directions.
 8. The rotor-stator structure of claim 6wherein said closed flux path passes through said first magnet and saidsecond magnet in substantially opposite directions.
 9. The rotor-statorstructure of claim 1 wherein first pole shoes for said number of fieldpole members form multiple air gaps with said first magnet.
 10. Therotor-stator structure of claim 1 wherein each of said first magnet andsaid second magnet establishes at least one air gap with each of saidfield pole members.
 11. The rotor-stator structure of claim 1 whereinsaid first magnet includes a first direction if polarization and saidsecond magnet includes a second direction of polarization, wherein saidfirst direction of polarization is substantially opposite to said seconddirection of polarization.
 12. The rotor-stator structure of claim 11wherein said first direction of polarization and said second directionof polarization exclude directions that are parallel to said axis ofrotation.
 13. The rotor-stator structure of claim 11 wherein said firstdirection of polarization and said second direction of polarization aresubstantially perpendicular to said axis of rotation.
 14. Therotor-stator structure of claim 13 wherein said first direction ofpolarization and said second direction of polarization are perpendicularto said axis of rotation.
 15. The rotor-stator structure of claim 11wherein said first direction of polarization and said second directionof polarization are configured to form flux path portions of a closedflux path within the interiors of said first magnet and said secondmagnet, respectively, said flux path portions each extending throughplanes that includes said axis of rotation.
 16. The rotor-statorstructure of claim 15 wherein at least one of said flux path portionsextends from one portion of said first conical surface to anotherportion of said first conical surface.
 17. The rotor-stator structure ofclaim 11 wherein said first direction of polarization and said seconddirection of polarization differ by an angle between 150 to 180 degrees.18. The rotor-stator structure of claim 1 wherein saji first magnet andsaid second magnet a dipole magnets.
 19. The rotor-stator structure ofclaim 1 wherein said rotor-stator structure is configured to receiveelectrical power as an electrical current into said at least one coilfor implementing an electric motor.
 20. The rotor-stator structure ofclaim 1 wherein said rotor-stator structure is configured to receivemechanical power as rotational motion about said shaft for implementingan electric generator.